Sealed magnetically operated flow control valve assembly

ABSTRACT

A sealed control valve assembly is provided for use in connection with a fluid valve having an inlet, an outlet and a flow control orifice hydraulically interposed therebetween for controlling the flow through the fluid valve. The valve assembly includes a sealed cylindrical isolator cap sealingly mounted to the fluid valve so that the chamber defined by the isolator cap is in hydraulic communication with the fluid valve. In one embodiment, an armature composed of a magnetic material is reciprocatably disposed within the isolator cap. A modulating plug is connected to a lower end of the armature to extend outside the isolator cap into the fluid valve adjacent the flow control orifice. A magnetic pole piece assembly, including a magnet sandwiched between a pair of pole pieces, is reciprocatably disposed outside and adjacent to the isolator cap. A diaphragm assembly is provided to move the pole piece assembly down in response to fluid pressure exerted against the diaphragm. The pressure against the diaphragm can be varied in relation to a condition of the fluid flowing through the fluid valve. The pole piece assembly and the armature form a magnetic circuit so that the armature follows the movement of the pole piece assembly in order to maintain the continuity of the magnetic circuit. The modulating plug moves with the armature to modulate the fluid flowing through the flow control orifice in the fluid valve. A biasing spring may be provided to react against the downward action of the diaphragm and provide a return stroke for the pole piece assembly and armature.

BACKGROUND OF THE INVENTION

The present invention relates to magnetically operated valves, such asfluid control valves. In particular, the invention concerns afluid-tight flow control valve which includes a valve stem sealed withina valve housing that is magnetically actuated.

Magnetically operated fluid valves are known in the prior art whichinclude an actuator movable between an on position and an off positionin response to a magnetic field. For example, the patent to Halgreen,U.S. Pat. No. 3,326,511, discloses an electro magnetically actuatedvalve in which an armature is affixed to a valve stem. When an electriccoil is activated, the magnetic flux causes the valve to move between anopen and closed position. The Halgreen patent also shows a sealedcylinder in which the magnetic actuator and valve stem reciprocates inresponse to the generator magnetic field.

The patent to Cummings et al., U.S. Pat. No. 4,779,640, discloses amagnetically operated automatic drain valve. In the Cummings device, afloat carries a permanent magnet that surrounds a closed valve housing.The pilot actuator reciprocates within that closed valve housing inresponse to the position of the permanent magnet relative to the pilotvalve plug. Again, the Cummins et al. patent discloses an on-off typedevice.

The patent to Parodi et al., U.S. Pat. No. 3,666,231, discloses anelectro magnetic valve which includes at least three windings which canbe selectively excited. The selective excitation of the windings causesthe valve to move between on and off positions depending upon whichcoils have been excited. Richeson, Jr., U.S. Pat. No. 4,831,973,discloses a similar valve that uses electromagnetic repulsion to move anarmature. Bosley et al., U.S. Pat. No. 4,690,371, shows anelectromagnetic valve with a permanent magnet armature. The valve opensor closes depending upon the electromagnet coil polarity.

Staefa Control System, Inc. of San Diego, Calif. manufactures athree-way modulating valve that uses an electromagnet oil to shuttle avalve disc between two positions to selectively connect one of twoinputs to the output.

There is a need to provide a sealed valve assembly which can operate inresponse to a sensed condition. For instance, a flow control valve mustvary the amount of fluid passing through a pipe in response to a fluidflow rate sensed down stream from the valve. The valve must be fluidtight so that the actuating member is free to reciprocate without riskof fluid leakage. There is also a need for a sealed valve that can beactuated in step-wise or continuously variable fashion, rather thansimply an on-off manner.

SUMMARY OF THE INVENTION

In view of the limitations of the prior art devices and of the needs inthe industry, the present invention provides a sealed control valveassembly for use in connection with a fluid valve having an inlet, anoutlet and a flow control orifice hydraulically interposed therebetweenfor controlling the flow through the fluid valve. The valve assemblyincludes a sealed cylindrical isolator cap sealingly mounted to thefluid valve so that the chamber defined by the isolator cap is inhydraulic communication with the fluid valve. In one embodiment, anarmature composed of a magnetic material is reciprocatably disposedwithin the isolator cap. A modulating plug is connected to a lower endof the armature to extend outside the isolator cap into the fluid valveadjacent the flow control orifice. A magnetic pole piece assembly,including a magnet sandwiched between a pair of pole pieces, isreciprocatably disposed outside and adjacent to the isolator cap. Adiaphragm assembly is provided to push the pole piece assembly down inresponse to fluid pressure exerted against the diaphragm. The pressureagainst the diaphragm is varied in relation to a condition of the fluidflowing through the fluid valve.

The pole piece assembly and the armature form a magnetic circuit so thatthe armature follows the movement of the pole piece assembly in order tomaintain the continuity of the magnetic circuit. That is, when thediaphragm flexes, the pole piece assembly moves downward toward thefluid valve. The armature moves downward within the isolator cap indirect relation to the movement of the pole piece assembly. As thearmature moves downward, it moves the modulator plug into the flowcontrol orifice, thereby controlling the flow of fluid through the fluidvalve. A biasing spring may be provided to react against the downwardaction of the diaphragm and provide a return stroke for the pole pieceassembly and armature.

In another embodiment, a rotary control valve assembly is provided forcontrolling a ball valve in a fluid valve. In this embodiment, the polepiece assembly is rotatably disposed within the sealed isolator cap. Astem connects the pole piece assembly to the ball valve so that the ballvalve rotates with the pole piece assembly. An armature cage is disposedover the isolator cap. Means, such as an electric motor, are provided torotate the armature cage relative to the isolator cap. As in theprevious embodiment, the armature cage and pole piece assembly form amagnetic circuit. Thus, as the armature cage is rotated by the electricmotor, the pole piece assembly likewise rotates within the isolator cap,thereby rotating the ball valve to control the fluid flow through thefluid valve.

It is one object of the present invention to provide sealed fluid flowcontrol valve that can be condition responsive. It is a further objectto provide such a valve that is capable of step-wise or continuouslyvariable operation.

Still another object of the invention is to provide a flow control valvethat is magnetically actuated. A further object is to provide such avalve assembly that is simple to assemble and repair yet capable ofefficient fluid-tight operation. Other objects and benefits of thepresent invention will become apparent when the following writtendescription and accompanying figures are considered.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a side cross sectional view of one embodiment of a linearlyactuated valve assembly according to the present invention.

FIG. 2 is an exploded isometric view of the valve assembly of FIG. 1shown in a disassembled configuration.

FIG. 3 is a side cross sectional view of the valve assembly of FIG. 1used in connection with a valve body and fluid conduit.

FIG. 4 is a side cross sectional view of a second embodiment of alinearly actuated valve assembly of the present invention.

FIG. 5 is a side cross sectional view of one embodiment of a rotaryactuated valve assembly according to the present invention.

FIG. 6 is an exploded isometric view of the valve assembly of FIG. 5shown in a disassembled configuration.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

For the purposes of promoting an understanding of the principles of theinvention, reference will now be made to the embodiment illustrated inthe drawings and specific language will be used to describe the same. Itwill nevertheless be understood that no limitation of the scope of theinvention is thereby intended, such alterations and furthermodifications in the illustrated device, and such further applicationsof the principles of the invention as illustrated therein beingcontemplated as would normally occur to one skilled in the art to whichthe invention relates.

In one embodiment of the present invention, shown in FIG. 1 a flowcontrol valve assembly 10 includes a housing 11 consisting of an upperhousing portion 12 and a lower housing portion 13. The upper and lowerhousing portions are joined by a pair of oppositely located arms 11a. Asshown more clearly in FIG. 2, the upper and lower housing portions 12and 13 are generally cylindrical in configuration. The arms 11aconnecting the housing portions define a gap between the two portionsthrough which the remaining components of the flow control valveassembly can be readily viewed and accessed.

An adaptor body 14 is connected to the lower housing portion 13. Theadaptor body includes a threaded connection for engagement with astandard valve body, such as the valve body 90 shown in FIG. 3. Theadaptor body 14 is connected to the lower housing portion 13 by way of apair of roll pins 16 that are seated within a bore formed by a pair ofpin channels. A first pair of pin channel 17 is formed in the outercircumference of the actuator body 14. A second pair of pin channels 18is formed in the lower housing portion 13, preferably by drilling alonga chord passing through the lower housing portion 13, as shown moreclearly in FIG. 2. Since no fluid passes outside of the adaptor body 14it is not essential that the connection between the adaptor body 14 andthe housing 11 be fluid-tight.

The flow control valve assembly 10 further includes a cover 20 which isengaged at a flange 21 to a flange 25 at the upper housing portion 12.The cover is connected to the upper housing portion 12 by way of severalself-tapping screws 26. Sandwiched between the cover 20 and the upperhousing portion 12 is a diaphragm 23. The diaphragm 23 includes a numberof mounting openings 24 through which the self-tapping screws 26 maypass when the cover is mounted on the housing.

In the present embodiment, the diaphragm 23 includes a circumferentialfold portion 29 and a preform portion 30 which assumes the shape of acup, as shown in FIG. 2. In the preferred embodiment, the diaphragm ismade of rubber so that it can be easily and repeatedly flexed. When thediaphragm is mounted between the housing 11 and the cover 20, a pressurecavity 33 is formed between the cover and the diaphragm surface. Apressure inlet 34, to which a fitting 35 is attached, opens into thepressure cavity 33. A separate pressure tube, such as tube 99 in FIG. 3,can be attached to the fitting 35 to provide a fluid under pressure tothe cavity 33.

A principal component of the flow valve assembly 10 is the modulatingplug 40 at the base of the assembly. The plug is internally threaded at41 so that a threaded tip 43 of a stem 42 can be engaged therein. Thestem slides axially within an actuation bore 15 through the adaptor body14. The stem 42 includes a pair of ring grooves 44 which receive a pairof glide seals 48 therein. The glide seals can be composed of TEFLON® orother similar bearing-type material which permits easy sliding of thestem 42 relative to the actuation bore 15 of the adaptor body 14. Duringnormal operation, the glide seals 48 remain seated within the actuationbore 15 as the stem reciprocates through the bore. The glide seals mayprovide some fluid sealing, although the seals 48 are not necessarilyprovided for that purpose. The primary object of the glide seals 48 isto provide a wear surface for the reciprocating motion of the stem 42and modulating plug 40. The glide rings can also be used to keep solidsfrom entering the chamber. The glide seals 48 can be readily removed andreplaced when they become worn.

In another aspect of the invention, an isolator cap 50 is mounted over amounting boss 52 on the adaptor body 14. In the present embodiment, theisolator cap 50 is a non-magnetic stainless steel cylinder that can besilver soldered, welded or pressure fitted onto the mounting boss 52.Alternatively, the cap 50 can be composed of TEFLON® a similarnon-magnetic corrosion-resistant material. It is important that theconnection between the isolator cap 50 and the mounting boss 52 befluid-tight. A plug 54 is attached in fluid-tight engagement at the topend of the isolator cap 50 to form a chamber 51. In the preferredembodiment, the plug is also formed of stainless steel and is silversoldered to the isolator cap 50. The plug 54 includes a snap ring grooveabove the isolator cap 50 within which a retaining ring or snap ring 58is engaged.

An armature spool 60 is disposed within the chamber 51 formed by theisolator cap 50 and plug 54. The lower end of the armature spool 60includes a threaded post 61 which is engaged with an internally threadedupper end of the stem 42. The armature spool 60 and stem 42 are adaptedto configured within the isolator cap 50. The armature spool 60 iscomposed of a ferro-magnetic material, such as 1018 low carbon steel.The stem 42 can be composed of stainless steel or another non-magneticmaterial.

Disposed around the isolator cap 50 is a pole piece assembly 65. In thepresent embodiment, the pole piece assembly 65 includes a ring magnet 66that is bounded on its upper and lower faces by a lower pole piece 68and an upper pole piece 69. The lower and upper pole pieces 68 and 69,respectively are held together by a number of assembly screws 70. Thelower and upper pole pieces 68 and 69 are disc-shape while the magnet 66is formed as an annular ring. Thus, the assembly screws 70 can besituated to contact the inner diameter of the magnet ring 66 to hold itin position relative to the isolator cap 50, rather than passingdirectly through the magnet. The lower and upper pole pieces 60 and 69are composed of a magnetic material, such as 1018 low carbon steel. Thering magnet 66 is readily commercially available, such an Alnico 5cylinder magnet sold as part no. 5G133 by Arnold Engineering Company.The pole piece assembly 65 is adapted to reciprocate about the exteriorof the isolator cap 50.

A diaphragm cup 75 is provided and is received within the preformportion 30 of the diaphragm 23. A number of stand-offs 77 are affixed tothe underside of the diaphragm cup 75 by recessed screws 79, as shown inFIG. 1. The stand-offs 77 contact the upper pole piece 69 to push thepole piece assembly 65 down as the diaphragm cup 75 moves downward. Aspacer 82 is situated between the upper pole piece 69 and the retainingsnap ring 58 to prevent the pole piece assembly 65 from moving beyondthe end of the isolator cap 50. A biasing spring 85 is disposed betweenthe lower pole piece 68 and the adaptor body 14 to bias the pole pieceassembly 65 upward toward the top of the isolator cap 50 when nopressure is applied to the diaphragm.

In the operation of the fluid control valve assembly 10 of the presentinvention, the pole piece assembly 65 and the armature spool 60 providea continuous magnetic circuit. The magnetic flux generated by the ringmagnet 66 follows the upper and lower pole pieces 68 and is closed bythe magnetic material armature spool 60. Thus, as the pole pieceassembly 65 reciprocates outside the isolator cap 50, the armature spool60 is naturally drawn to move with the pole piece assembly 65 in orderto maintain the continuity of the magnetic circuit. In this embodiment,the pole piece assembly 65 is the prime mover; that is, the armaturespool 60 moves in response to motion of the pole piece assembly 65. Asthe armature spool 60 moves, the stem 42 and modulating plug 40 alsomove.

The diaphragm 23 provides the primary motive force for moving the polepiece assembly 65 downward relative to the isolator cap 50. As pressureP (FIG. 3) is applied through the pressure inlet 34 into the cavity 33,the diaphragm 23, and particularly the preform portion 30, flexesdownward along the circumferential fold 29. AS the diaphragm 23 deflectsit pushes the diaphragm cup 75 downward. The standoffs 77, connected tothe cup 75 push against the upper pole piece 69 of the pole pieceassembly 65. The force due to the pressure P acting against thediaphragm and moving the pole piece assembly 65 downward reacts againstthe spring force of the biasing spring 85 to compress the spring 85. Inaddition, as the pole piece assembly 65 moves downward, the armaturespool 60 follows thereby moving the modulating plug 40 downward into avalve body, such as valve body 90 shown in FIG. 3. When the pressure Pin the cavity 33 is reduced, the biasing spring 85 pushes the pole pieceassembly 65 and diaphragm cup 75 upward until the spacer 82 contacts theretaining snap ring 58 at the top of the isolator cap 50. The travel ofthe pole piece assembly 65 is limited by the snap ring 58 at the top ofthe isolator cap and by the lower housing portion 13 at the bottom endof the isolator cap.

In one specific embodiment, the biasing spring 85 has a spring constantof 90 lb./in. The diaphragm 23 has a working area of about 7 in.² sothat a closing pressure in cavity 33 of about 8 p.s.i. will produce anarmature travel of about 0.5 in. The magnet 66 in this specificembodiment has an outer diameter of 2 in., an inner diameter of 1.5 in.and a height of 1 in. and provides a force of 625 oersted. The cap 50has a thickness wall of 0.030 in. so the gap between the pole pieces andarmature is minimal to reduce flux losses.

One application of the flow control valve assembly 10 of the presentinvention is shown in FIG. 3. In this application, the valve assembly 10is mounted to a valve body 90. The valve body 90 includes an inlet 91and an outlet 92 with a flow control orifice 94 providing fluidcommunication between the inlet F_(in) and the outlet F_(out). Anadaptor 95, having a bore 96 therethrough, is threaded into the flowcontrol orifice 94 to minimize the armature stroke necessary to closethe bore. In the present embodiment, the modulating plug 40 has atapered configuration so that the amount of restriction of flow throughthe bore 96 is variable.

The outlet 92 of the valve body 90 is connected to a conduit 97.Downstream of the flow control valve assembly 10 in the conduit 97 is asensor 98. The sensor 98 can sense some condition of the fluid passingthrough the conduit 97. For instance, the sensor may determine the flowrate, the pressure or the fluid temperature. The sensor includes apneumatic or hydraulic actuator which discharges a fluid under pressurethrough the pressure tube 99. The pressure tube 99 is connected to thefitting 95 to provide fluid pressure through the pressure inlet 34 intothe cavity 33. Thus, in this application, the sensor 98 senses aparticular condition of the fluid passing through the conduit 97 andvaries the pressure in the pressure cavity 33 by way of a fluid throughthe pressure tube 99. A constant adjustment of the fluid F_(out) flowingthrough the bore 96 and outlet 92 can then be achieved by modulating thepressure operating against the diaphragm 23 in response to the sensedcondition.

The present invention provides a device for controlling fluid flowthrough a valve body in response to a sensed condition. The flow controlvalve assembly 10 provides a leak-proof configuration in which theactuator (armature 60 and stem 42) reciprocates within a completelysealed cavity, such as chamber 51 within isolator cap 50. Any fluid thatleaks past the glide seals 48 in trapped within chamber 51. The use ofthe pole piece assembly 65 and the magnetically coupled armature spool60 permits actuation where there is no physical connection between theprime-mover and the actuated stem 42 and modulating plug 40.

In a second embodiment of the invention, shown in FIG. 4, a flow controlvalve assembly 110 is provided which is similiar in function andoperation to the flow control valve 10 of the previous embodiment. Thevalve assembly 110 includes a housing 111 which can have an openconfiguration similiar to the previous housing 11. In a variation fromthe first embodiment, the flow control valve assembly 110 includes acompression nut 116. The compression nut 116 is connected to the housing111 by way of a number of set screws 118 engaged in bores 117 in thecompression nut. The valve assembly 110 further includes a cover 120 anda diaphragm 123 that is similar to the cover and diaphragm of theprevious embodiment. A pressure cavity 133 is defined between thediaphragm and the cover and is fed by a pressure inlet 134 through thecover 120.

The flow control valve assembly 110 includes a compression adaptor 114which is threaded at its bottom end for connection to a flow valve aswith the former embodiment. The compression adaptor 114 includes a bore115 through which a stem 142 is reciprocated. A bushing 148 can bemounted within the bore 115 to reduce the sliding friction between thestem and the compression adaptor 114. A modulating plug 140 is affixedat the end of a stem 142.

The flow control valve assembly 110 includes an isolator cap 150 in theshape of a closed-end cylinder. Opposite the closed end is a flaredportion 151. The flared portion 151 is engaged between similarlyconfigured portions of the compression adaptor 114 and compression nut116. The compression adaptor 114 can be threaded into the nut 116thereby exerting pressure against the flared portion 151 to retain theisolator cap in a fluid-tight arrangement.

As in the previous embodiment, an armature spool 160 is connected to theend of the stem 142 and reciprocates within the isolator cap 150. Inthis embodiment, however, the end of the cap is closed thereby providingthe upper limit to the motion of the armature spool 160, stem 142 and,consequently, the modulating plug 140. The pole piece assembly 165includes a number of magnetic rings 166 which are engaged between alower pole piece 168 and an upper pole piece 169. The pole pieceassembly 165 is mounted within a collar 178 of a diaphragm cup 175. Thediaphragm cup 175 is engaged within the diaphragm 123. The diaphragm cup175 includes a cylindrical cavity 176 which permits the diaphragm cup175 to reciprocate over the outside of the isolator cap 150.

The diaphragm cup 175 includes a collar 178 to which the pole pieceassembly 165 is affixed. A number of guide rods 182 pass through thelower portion of the housing 111 and are engaged, preferably by threads,to the underside of the diaphragm cup 175. The ends of the guide rods182 are formed into stops 183 which react against the outside of thehousing 111 to prevent further upward motion of the diaphragm cup 175. Abiasing spring 185, similar to the spring 85 previously described, isprovided to bias the pole piece assembly and diaphragm cup to an upward,normally open position.

The collar 178 of the diaphragm cup 175 reciprocates within a bore 172in the lower part of the housing 112. The travel of the diaphragm cupand collar 178 is limited at the bottom of their stroke by thecompression nut 116. The flow control valve assembly 110 operates andfunctions in a manner nearly identical to the valve assembly 10 of theprevious embodiment.

In another embodiment of the invention, illustrated in FIGS. 5 and 6, arotary actuated valve assembly 210 is provided. The valve assembly 210is shown mounted on a conventional valve body 290 which includes a ballvalve 240. The ball valve 240 includes a flow control orifice 294 whichconnects the inlet 291 and the outlet 292 of the valve body 290. Anaccess plug 293 is threaded into the base of the valve body 290 topermit assembly of the ball valve within the body. Flow through thevalve body 290 is controlled by rotating the ball valve 240 within thebody to increase or decrease the portion of the flow control orifice 294open between the inlet and outlet.

Actuation of the ball valve 240 is accomplished through a stem 242 whichis engaged at end 243 to the ball valve, preferably as a threadedengagement. The stem 242 rotates within a bushing 248 mounted in anactuation bore 247 in the valve body 290. The bushing 248 is preferablycomposed of a resin, such as a polytetrafluoroethylene (TEFLON® forinstance), although other materials, such as bronze, may be useddepending upon the application for the rotary valve assembly 210. Thestem 242 is preferably composed of a non-magnetic corrosion-resistantmaterial, such as stainless steel.

A pole piece assembly 265 is axially disposed along the stem 242. Thepole piece assembly 265 includes a cylindrical magnet 266 sandwichedbetween a lower pole piece 268 and an upper pole piece 269. The stem 242includes a keyed portion 242a which fits through correspondingly shapedkeyed bores 266a, 268a and 269a in the magnet, lower pole piece andupper pole piece, respectively. The keyed relationship between the stemportion 242a and the bores 266a, 268a and 269a allows the stem and polepiece assembly to rotate as a unit. In the preferred embodiment, thepole pieces are composed of a magnetic material, such as 1018 low carbonsteel, while the magnet 266 is a cast Alnico 8 magnet from ArnoldEngineering.

The stem 242 includes a shoulder 246 formed at the base of the keyedportion 242a which supports the lower pole piece 268 and, consequently,the entire pole piece assembly 265. The shoulder 246 is displacedslightly above the surface of the valve body to avoid frictional contactbetween the lower pole piece 268 and the body 290. The pole pieceassembly is held in position on the stem by a nut 245 threaded onto athreaded tip 244 of the stem.

An isolator cap 250 surrounds the pole piece assembly 265 and stem 242.The cap 250 comprises a non-magnetic stainless steel cylinder which issuitably sealingly affixed to a mounting boss 252 of the valve body 290.The open top of the cap cylinder 250 is closed by a non-magnetic plug254 which is sealingly engaged to the cap, such as by brazing orwelding. The engagement between the cap 250 and the mounting boss 252and plug 254 provides a leak-proof seal for the interior of the cap.Thus, any fluid leakage from the valve body 290 through the actuationbore 247 and into the cap 250 is completely contained within the cap.

While the pole piece assembly (65 and 165) of the linear actuated valveassemblies (10 and 110) are the prime movers, the pole piece assembly265 of the rotary actuated valve assembly 210 operates as a follower. Inthis embodiment, the armature cage 260 is the prime mover--that is, thepole piece assembly 265 follows the movement of the armature cage 260.The armature cage 260 surrounds the isolator cap 250 and rides upon aball bearing assembly 258 supported in a bearing track 256 at the topsurface of the plug 254. A shoulder bolt 261 passes through a bearingbore 262 in the armature cage 260 and is threaded into a bore 255 in theplug 254. The shoulder bolt 261 retains the armature cage 260 over theisolator cap 250 and provides a bearing surface for smooth rotation ofthe cage 260 relative to the cap 250.

In the preferred embodiment, the armature cage 250 includes a keyedcoupling bore 297 to be drivenly engaged to a prime mover (not shown).The valve body 290 includes a mounting surface 296 on which the primemover may be mounted. In the preferred embodiment, the prime mover is anelectric gear motor which, in essence, replaces the pressure diaphragmarrangement of the linearly actuated embodiments. The motor can beconnected to a sensor/controller, such as the sensor 198 depicteddownstream of the valve body in FIG. 2.

The armature cage 260 includes evenly spaced apart vertically orientedlegs 264. The lower and upper pole pieces 268 and 269 each includecorrespondingly located pole arms 268b and 269b, respectively. Thearmature legs 264 and pole arms 268b and 269b define a magnetic circuitfor the magnetic flux generated by the magnet 266. The gaps between thearmature legs 264 tend to concentrate the magnetic field in the legs 264and arms 268b and 269b. As the armature cage 260 rotates the pole pieceassembly 265 has a tendency to rotate with the cage in order to maintainthe flux path established between the legs 264 and the arms 268b and269b. As the pole piece assembly rotates, so does the stem 242 and theball valve 240 to which the stem is attached, thereby effectingcontrolled opening and closing of the flow control orifice 294.

In an alternative version of the present embodiment, shown in FIG. 7, arotary valve assembly 210', which is substantially similar to theassembly 210, includes a torsion spring 285 to bias the pole pieceassembly 265' and, consequently, the ball valve 240' to a particularorientation. The torsion spring 285 includes ends 285a and 285b whichfit into connection holes 286 and 287 in the lower pole piece 268' andmounting boss 252', respectively. Alternatively, the spring can bedisposed between the plug 254' at the top of the isolator cap 250' andthe upper pole piece 269'. The torsion spring 285 can be calibrated andpositioned so that in its free state the spring biases the ball valve240' to a closed position, for example.

The flow control valve assemblies 10, 110 and 210 of the presentinvention can have many applications. The assemblies can be used toprovide fluid control of water or corrosive chemicals, for instance, inan industrial process. A primary benefit of the present invention isthat the valve assembly is positively sealed against leakage of thefluid to be monitored and/or controlled. The valve assemblies of thepresent invention can operate simply as an on-off valve, but are bestsuited for applications requiring step-wise or continuously variableoperation between an on and an off position. The present invention canalso be adapted to control a three-way mixing valve. The rotary actuatedembodiment is particularly well-suited for the three-way valveapplication by simply substituting a three-way valve element and valvebody for the illustrated ball valve.

The characteristics of the specific elements of the magnetic circuitformed by the armature and pole piece assemblies of the severalembodiments are determined largely by the application to which thedevices are put. For instance, the strength of the magnets 66, 166 and266 must be sufficient to overcome the biasing springs 85, 185 and 285as well as the pressure of the fluid passing through the valve body andthe friction inherent with the motion of the stem. The force to breakthe magnetic bond between the armature and pole piece assembly must alsobe calibrated to the particular application to avoid decoupling betweenthe working members of the device.

While the invention has been illustrated and described in detail in thedrawings and foregoing description, the same is to be considered asillustrative and not restrictive in character. It is understood thatonly the preferred embodiments have been shown and described and thatall changes and modifications that come within the spirit of theinvention are desired to be protected.

For instance, while permanent magnets have been describedelectro-magnets may be substituted in appropriate applications of thisinvention. In another variation, the sensor 98 may be an electricalsensor, such as a transducer, that converts a sensed condition of thefluid into an electrical signal for use by a motor or an electricalcontroller.

With respect to the rotary actuated embodiment of FIGS. 5 and 6, it iscontemplated that the ball valve of valve body 290 is replaced withanother suitable rotary-type valve that is capable of continuouslyvarying the fluid flow through the valve. In addition, while the torsionspring 285 is shown engaging the pole piece assembly, it is alsocontemplated that the spring be disposed between the armature cage 250and the prime mover. In either instance, the prime mover can bedecoupled, either externally from the armature cage or internally byassuming a "free-wheeling" state.

What is claimed is:
 1. A sealed magnetic control valve assembly for usein connection with a fluid valve controlling flow through a conduit, thefluid valve having an inlet, an outlet and a flow control orificehydraulically disposed therebetween, the valve assembly comprising:asealed cylindrical isolator cap, composed of non-magnetic material,having a longitudinal length and defining a chamber open at one end;means for sealingly mounting said isolator cap at said one end to thefluid valve such that said chamber is in fluid communication with thefluid valve; an armature composed of a magnetic material andreciprocatably disposed within said chamber of said isolator cap; and amodulating plug connected to said armature to extend outside saidchamber through said one end and into the fluid valve adjacent the flowcontrol orifice when said isolator cap is mounted to the fluid valve,whereby modulation of said modulating plug within the flow controlorifice controls the flow of fluid through the outlet of the fluidvalve; a pole piece assembly reciprocatably disposed outside andadjacent to said isolator cap and including;a pair of opposite polepieces composed of a magnetic material; and a magnet disposed betweensaid opposite pole pieces; means for moving said pole piece assemblyalong the longitudinal length of said isolator cap. wherein saidarmature has a pair of opposite ends with a length substantially equalto the distance between said pair of opposite pole pieces; whereby saidarmature and said pole piece assembly define a magnetic circuit so thatwhen said pole piece assembly is moved along the longitudinal length ofsaid isolator cap, by said means for moving, said armature moves withinsaid isolator cap in direct relation thereto to maintain the magneticcircuit, such that said pair of opposite ends and said pair of oppositepole pieces are in direct alignment with each other in all positions ofsaid modulating plug; and further whereby said modulating plug moveswith said armature to vary fluid flow through the flow control orificeand the outlet of the fluid valve in relation to the movement of saidmodulating plug relative to the flow control orifice.
 2. The controlvalve assembly of claim 1, wherein said means for moving includes:adiaphragm; means for defining a cavity including said diaphragm; meansfor providing a pressurizing fluid under pressure to said cavity to flexsaid diaphragm in a first direction; and means for connecting saiddiaphragm to said pole piece assembly.
 3. The control valve assembly ofclaim 2, wherein said means for providing a pressurizing fluidincludes:means for sensing a condition of fluid flowing through theconduit; and means for varying the pressure of the pressurizing fluidprovided to said cavity in response to the sensed condition of the fluidflowing through the conduit.
 4. The control valve assembly of claim 2,wherein said means for moving further includes means for biasing saidpole piece assembly against reciprocation in a first direction.
 5. Thecontrol valve assembly of claim 4, wherein:said means for biasingincludes a spring operable to push said pole piece assembly in a seconddirection opposite said first direction; and said control valve assemblyfurther includes a retaining ring engaged about said isolator cap at theend opposite said open end for preventing motion of said pole pieceassembly in said second direction past said retaining ring.
 6. Thecontrol valve assembly of claim 1, wherein said magnet is a permanentmagnet.
 7. The control valve assembly of claim 1, wherein said means forsealingly mounting includes:an adapter body having a mounting boss andan actuation bore therethrough; wherein said isolator cap is removablysealingly engaged into said mounting boss; and further wherein saidmodulating plug extends through said actuation bore.
 8. The controlvalve assembly of claim 7, further comprising:a stem engaged at one endto said armature and at the other end to said modulating plug, andextending along the longitudinal length of said isolator cap and throughsaid actuation bore; and a number of glide seals disposed between saidstem and said actuation bore.
 9. The control valve assembly of claim 1,wherein said means for sealingly mounting includes:said isolator caphaving a flared portion at said open end; a compression adaptor havingmeans for engaging the fluid valve; a compression nut having means forengaging said compression adaptor with said flared portion of saidisolator cap sealingly engaged between said adaptor and said nut.
 10. Asealed magnetic control valve assembly for use in connection with arotary fluid valve controlling flow through a conduit, the fluid valvehaving an inlet, an outlet and a ball valve interposed therebetween inwhich the ball valve is rotatable within the fluid valve to control thefluid flowing therethrough, the valve assembly comprising:a sealedcylindrical isolator cap, composed of non-magnetic material, having alongitudinal length and defining a chamber open at one end; means forsealingly mounting said isolator cap at said one end to the fluid valvesuch that said chamber is in fluid communication with the fluid valve; apole piece assembly rotatably disposed within said isolator cap andincluding;a pair of opposite pole pieces compsed of a magnetic materialand having a plurality of pole arms; and a magnet disposed between saidopposite pole pieces; means for connecting said pole piece assembly tothe ball valve so that the ball valve is rotatable with said pole pieceassembly; an armature cage composed of a magnetic material and having aplurality of spaced apart legs corresponding to said plurality of polearms with a length substantially equal to the distance between said pairof opposite pole pieces, and rotatably disposed outside and adjacent tosaid isolator cap; and means for rotating said armature cage relative tosaid isolator cap; whereby said armature cage and said pole pieceassembly define a magnetic circuit so that when said armature cage isrotated outside said pole piece assembly rotates in direct relationthereto to maintain the magnetic circuit, such that said plurality oflegs and said plurality of pole arms are in direct alignment with eachother in all positions of said ball valve; and further whereby therotation of said pole piece assembly causes the ball valve to rotate tovary the flow of fluid through the outlet of the fluid valve in relationto the movement of said ball valve.
 11. The control valve assembly ofclaim 10, further comprising means for rotationally mounting saidarmature cage over said isolator cap including:a closed end of saidisolator cap; an inner surface of said armature cage disposed adjacentsaid closed end of said isolator cap; and bearing means between saidclosed end of said isolator cap and said inner surface of said armature.12. The control valve assembly of claim 10, wherein:each of saidopposite pole pieces is a disc having a keyed opening therethrough; saidmagnet is a cylindrical magnet having a keyed bore therethrough; andsaid means for connecting said pole piece assembly to the ball valveincludes;a stem having a keyed portion extending through andinterengaged with said keyed opening in each of said pole pieces andsaid keyed bore; means at one end of said stem for connecting said stemto the ball valve; and means at the other end of said stem for retainingsaid stem in interlocking engagement with said pole piece assembly. 13.The control valve assembly of claim 10, further including a torsionspring operably disposed between said isolator cap and said pole pieceassembly for biasing said pole piece assembly to a predeterminedorientation relative to said isolator cap.
 14. A sealed magnetic controlvalve assembly for use in connection with a fluid valve controlling flowthrough a conduit, the fluid valve having an inlet, an outlet and a flowcontrol orifice hydraulically disposed therebetween, the valve assemblycomprising:a sealed cylindrical isolator cap defining a chamber open atone end and composed of a non-magnetic material; means for sealinglymounting said isolator cap at said one end to the fluid valve such thatsaid chamber is in fluid communication with the fluid valve; amodulating plug; an armature composed of a magnetic material and movablerelative to said isolator cap; and a pole piece assembly movablerelative to said isolator cap and including;a pair of opposite polepieces composed of a magnetic material; and a magnet disposed betweensaid opposite pole pieces; means for moving one of said armature andsaid pole piece assembly relative to said isolator cap. wherein saidarmature has a pair of opposite ends with a length substantially equalto the distance between said pair of opposite pole pieces; wherein saidone of said armature and said pole piece assembly is disposed outsidesaid isolator cap, and the other of said armature and said pole pieceassembly is disposed within said chamber defined by said isolator capand is connected to said modulating plug; whereby said armature and saidpole piece assembly define a magnetic circuit so that when said one ofsaid armature and said pole piece assembly is moved by said means formoving, said other of said armature and said pole piece assembly movesin direct response thereto, such that said pair of opposite ends andsaid pair of opposite pole pieces are in direct alignment with eachother in all positions of said modulating plug; and further whereby saidmodulating plug moves with said other of said armature and said polepiece assembly to vary the flow of a fluid through the flow controlorifice and the outlet of the fluid valve in proportion to the amount ofmovement of said modulating plug relative to the flow control orifice.